Vanguard Mid-Cap Index Fund 

Summary Prospectus 

April 29, 2011 

Signal^®Shares 

Vanguard Mid-Cap Index Fund Signal Shares (VMISX) 

The Fund’s statutory Prospectus and Statement of Additional Information dated 

April 29, 2011, are incorporated into and made part of this Summary Prospectus 

by reference. 

Before you invest, you may want to review the Fund’s Prospectus, which 

contains more information about the Fund and its risks. You can find 

the Fund’s Prospectus and other information about the Fund online at 

www.vanguard.com/prospectus. You can also get this information at no 

cost by calling 800-662-7447 or by sending an e-mail request to 

online@vanguard.com. 

 

The Securities and Exchange Commission (SEC) has not approved or disapproved these securities or 

passed upon the adequacy of this prospectus. Any representation to the contrary is a criminal offense. 

Investment Objective
The Fund seeks to track the performance of a benchmark index that measures the
investment return of mid-capitalization stocks.

Fees and Expenses
The following table describes the fees and expenses you may pay if you buy and hold
Signal Shares of the Fund.

Shareholder Fees
(Fees paid directly from your investment)

Sales Charge (Load) Imposed on Purchases	None
Purchase Fee	None
Sales Charge (Load) Imposed on Reinvested Dividends	None
Redemption Fee	None

Annual Fund Operating Expenses
(Expenses that you pay each year as a percentage of the value of your investment)

Management Expenses	0.09%
12b-1 Distribution Fee	None
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.12%

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Example

The following example is intended to help you compare the cost of investing in the
Fund’s Signal Shares with the cost of investing in other mutual funds. It illustrates the
hypothetical expenses that you would incur over various periods if you invest $10,000
in the Fund’s shares. This example assumes that the Shares provide a return of 5% a
year and that operating expenses remain as stated in the preceding table. The results
apply whether or not you redeem your investment at the end of the given period.
Although your actual costs may be higher or lower, based on these assumptions your
costs would be:

1 Year	3 Years	5 Years	10 Years
$12	$39	$68	$154

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate
higher transaction costs and may result in higher taxes when Fund shares are held in
a taxable account. These costs, which are not reflected in annual fund operating
expenses or in the previous expense example, reduce the Fund’s performance. During
the most recent fiscal year, the Fund’s portfolio turnover rate was 16%.

Primary Investment Strategies
The Fund employs a “passive management”—or indexing—investment approach
designed to track the performance of the MSCI US Mid Cap 450 Index, a broadly
diversified index of stocks of medium-size U.S. companies. The Fund attempts to
replicate the target index by investing all, or substantially all, of its assets in the stocks
that make up the Index, holding each stock in approximately the same proportion as
its weighting in the Index.

Primary Risks
An investment in the Fund could lose money over short or even long periods. You should
expect the Fund’s share price and total return to fluctuate within a wide range, like the
fluctuations of the overall stock market. The Fund’s performance could be hurt by:

• Stock market risk, which is the chance that stock prices overall will decline. Stock
markets tend to move in cycles, with periods of rising prices and periods of falling prices.
The Fund’s target index may, at times, become focused in stocks of a particular sector,
category, or group of companies. Because the Fund seeks to track its target index, the
Fund may underperform the overall stock market.

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• Investment style risk, which is the chance that returns from mid-capitalization
stocks will trail returns from the overall stock market. Historically, mid-cap stocks have
been more volatile in price than the large-cap stocks that dominate the overall market,
and they often perform quite differently. Mid-cap stocks tend to have greater volatility
than large-cap stocks because, among other things, medium-size companies are more
sensitive to changing economic conditions.

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed
by the Federal Deposit Insurance Corporation or any other government agency.

Annual Total Returns
The following bar chart and table are intended to help you understand the risks of
investing in the Fund. The bar chart shows how the performance of the Fund‘s Signal
Shares has varied from one calendar year to another over the periods shown. The
table shows how the average annual total returns of the Signal Shares compare with
those of the Fund‘s target index, which has investment characterisitcs similar to those
of the Fund. Keep in mind that the Fund’s past performance (before and after taxes)
does not indicate how the Fund will perform in the future. Updated performance
information is available on our website at vanguard.com/performance or by calling
Vanguard toll-free at 800-662-7447.

Annual Total Returns — Vanguard Mid-Cap Index Fund Signal Shares

During the periods shown in the bar chart, the highest return for a calendar quarter
was 21.54% (quarter ended September 30, 2009), and the lowest return for a quarter
was –25.62% (quarter ended December 31, 2008).

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Average Annual Total Returns for Periods Ended December 31, 2010

		Since
		Inception
		(Mar. 30,
	1 Year	2007)
Vanguard Mid-Cap Index Fund Signal Shares
Return Before Taxes	25.62%	1.11%
Return After Taxes on Distributions	25.39	0.84
Return After Taxes on Distributions and Sale of Fund Shares	16.93	0.87
MSCI US Mid Cap 450 Index
(reflects no deduction for fees, expenses, or taxes)	25.69%	1.13%

Actual after-tax returns depend on your tax situation and may differ from those shown in
the preceding table. When after-tax returns are calculated, it is assumed that the
shareholder was in the highest individual federal marginal income tax bracket at the time
of each distribution of income or capital gains or upon redemption. State and local
income taxes are not reflected in the calculations. Please note that after-tax returns are
not relevant for a shareholder who holds fund shares in a tax-deferred account, such as
an individual retirement account or a 401(k) plan. Also, figures captioned Return After
Taxes on Distributions and Sale of Fund Shares will be higher than other figures for the
same period if a capital loss occurs upon redemption and results in an assumed tax
deduction for the shareholder.

4

Investment Advisor
The Vanguard Group, Inc.

Portfolio Manager

Donald M. Butler, CFA, Principal of Vanguard. He has managed the Fund since its
inception in 1998.

Purchase and Sale of Fund Shares
You may purchase or redeem shares online through our website (vanguard.com), by
mail (The Vanguard Group, P.O. Box 1110, Valley Forge, PA 19482-1110), or by telephone
(800-662-2739). Signal Shares generally are available to certain institutional and financial
intermediary clients with no minimum initial or subsequent investment requirements.

Tax Information
The Fund’s distributions may be taxable as ordinary income or capital gain. Distributions
are taxable to you for federal income tax purposes, whether or not you reinvest these
amounts in additional Fund shares. A sale or exchange of Fund shares is a taxable
event, which means that you may have a capital gain to report as income, or a capital
loss to report as a deduction, when you complete your federal income tax return.
Dividend and capital gains distributions that you receive, as well as your gains or losses
from any sale or exchange of Fund shares, may also be subject to state and local
income taxes.

Payments to Financial Intermediaries
The Fund and its investment advisors do not pay financial intermediaries for sales of
Fund shares.

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Vanguard Mid-Cap Index Fund Signal Shares—Fund Number 1344

CFA^® is a trademark owned by CFA Institute.

THIS FUND IS NOT SPONSORED, ENDORSED, SOLD OR PROMOTED BY MSCI INC. (“MSCI”), ANY OF ITS AFFILIATES, ANY
OF ITS DIRECT OR INDIRECT INFORMATION PROVIDERS OR ANY OTHER THIRD PARTY INVOLVED IN, OR RELATED TO,
COMPILING, COMPUTING OR CREATING ANY MSCI INDEX (COLLECTIVELY, THE “MSCI PARTIES”). THE MSCI INDEXES ARE
THE EXCLUSIVE PROPERTY OF MSCI. MSCI AND THE MSCI INDEX NAMES ARE SERVICE MARK(S) OF MSCI OR ITS
AFFILIATES AND HAVE BEEN LICENSED FOR USE FOR CERTAIN PURPOSES BY VANGUARD. NONE OF THE MSCI PARTIES
MAKES ANY REPRESENTATION OR WARRANTY, EXPRESS OR IMPLIED, TO THE OWNERS OF THIS FUND OR ANY MEMBER
OF THE PUBLIC REGARDING THE ADVISABILITY OF INVESTING IN FUNDS GENERALLY OR IN THIS FUND PARTICULARLY OR
THE ABILITY OF ANY MSCI INDEX TO TRACK CORRESPONDING STOCK MARKET PERFORMANCE. MSCI OR ITS AFFILIATES
ARE THE LICENSORS OF CERTAIN TRADEMARKS, SERVICE MARKS AND TRADE NAMES AND OF THE MSCI INDEXES
WHICH ARE DETERMINED, COMPOSED AND CALCULATED BY MSCI WITHOUT REGARD TO THIS FUND OR THE ISSUER OR
OWNER OF THIS FUND. NONE OF THE MSCI PARTIES HAS ANY OBLIGATION TO TAKE THE NEEDS OF THE ISSUERS OR
OWNERS OF THIS FUND INTO CONSIDERATION IN DETERMINING, COMPOSING OR CALCULATING THE MSCI INDEXES.
NONE OF THE MSCI PARTIES IS RESPONSIBLE FOR OR HAS PARTICIPATED IN THE DETERMINATION OF THE TIMING OF,
PRICES AT, OR QUANTITIES OF THIS FUND TO BE ISSUED OR IN THE DETERMINATION OR CALCULATION OF THE
CONSIDERATION INTO WHICH THIS FUND IS REDEEMABLE. NONE OF THE MSCI PARTIES HAS ANY OBLIGATION OR
LIABILITY TO THE OWNERS OF THIS FUND IN CONNECTION WITH THE ADMINISTRATION, MARKETING OR OFFERING OF
THIS FUND.
ALTHOUGH MSCI SHALL OBTAIN INFORMATION FOR INCLUSION IN OR FOR USE IN THE CALCULATION OF THE MSCI INDEXES
FROM SOURCES WHICH MSCI CONSIDERS RELIABLE, NONE OF THE MSCI PARTIES WARRANTS OR GUARANTEES THE
ORIGINALITY, ACCURACY AND/OR THE COMPLETENESS OF ANY MSCI INDEX OR ANY DATA INCLUDED THEREIN. NONE OF
THE MSCI PARTIES MAKES ANY WARRANTY, EXPRESS OR IMPLIED, AS TO RESULTS TO BE OBTAINED BY LICENSEE,
LICENSEE’S CUSTOMERS OR COUNTERPARTIES, ISSUERS OF THE FUNDS, OWNERS OF THE FUNDS, OR ANY OTHER PERSON
OR ENTITY, FROM THE USE OF ANY MSCI INDEX OR ANY DATA INCLUDED THEREIN IN CONNECTION WITH THE RIGHTS
LICENSED HEREUNDER OR FOR ANY OTHER USE. NONE OF THE MSCI PARTIES SHALL HAVE ANY LIABILITY FOR ANY ERRORS,
OMISSIONS OR INTERRUPTIONS OF OR IN CONNECTION WITH ANY MSCI INDEX OR ANY DATA INCLUDED THEREIN. FURTHER,
NONE OF THE MSCI PARTIES MAKES ANY EXPRESS OR IMPLIED WARRANTIES OF ANY KIND, AND THE MSCI PARTIES HEREBY
EXPRESSLY DISCLAIM ALL WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, WITH RESPECT TO
ANY MSCI INDEX AND ANY DATA INCLUDED THEREIN. WITHOUT LIMITING ANY OF THE FOREGOING, IN NO EVENT SHALL
ANY OF THE MSCI PARTIES HAVE ANY LIABILITY FOR ANY DIRECT, INDIRECT, SPECIAL, PUNITIVE, CONSEQUENTIAL OR
ANY OTHER DAMAGES (INCLUDING WITHOUT LIMITATION LOST PROFITS) EVEN IF NOTIFIED OF THE POSSIBILITY OF
SUCH DAMAGES.

© 2011 The Vanguard Group, Inc. All rights reserved.
Vanguard Marketing Corporation, Distributor.
	SP 1344 042011